Compact economical spark arrestor and muffler

The invention relates to spark arrestors and mufflers, and more particularly to screen-type spark arrestors including within a muffler.

Conventional stator-type spark arrestors take up internal muffler volume because of the numerous components necessary to operation. For this same reason, the restriction of the muffler is increased along with the muffler cost because of the added parts.

The present invention arose during efforts to meet a need for a low cost, easily manufactured high performance spark arrestor for a variety of applications, including an ATV, all-terrain vehicle. Such product must meet USDA Standard 5100-1b for spark arrestors for internal combustion engines. This is accomplished in the present invention in a particularly desirable, simple, and low cost manner. In a particularly desirable aspect, the invention enables the use of known elements in combination, including a screen member for blocking carbon particles and preserving performance as well as keeping cost down, star-crimping, and ring crimping.

FIG. 1 is a side elevation view of a muffler in accordance with the invention.

FIG. 2 is a side elevation view of one of the component parts of the muffler of FIG. 1 .

FIG. 3 is a left end elevation view of the component of FIG. 2 .

FIG. 4 is a side sectional exploded view of the component of FIG. 2 .

FIG. 5 is an assembled view of the structure of FIG. 4 .

FIG. 6 is an enlarged view of a portion of FIG. 5 along line 6 — 6 .

FIG. 7 is a sectional view taken along line 7 — 7 of FIG. 5 .

FIG. 1 shows a muffler 10 having a housing 12 for silencing exhaust flowing from a housing inlet 14 to a housing outlet 16 . The housing has a pair of hanger brackets 18 and 20 . The muffler includes internal silencing structure His known, and does not form part of the present invention. One of the inlet and outlet, preferably the outlet, includes a flange 22 mounted to and closing the housing. The flange has an exhaust pipe 24 mounted thereto. The pipe has an interior portion 26 , FIGS. 2, 4 , 5 , within housing 12 , and an exterior portion 28 outside of the housing. Interior portion 26 of the pipe extends axially along an axis 30 , FIG. 5, to an inner end 32 . A tubular screen spark arrestor 34 is coaxial with interior portion 26 and extends axially along axis 30 between a first closed end 36 axially spaced inwardly from inner end 32 of the pipe, and a second distally opposite end 38 axially overlapping the pipe and extending past inner end 32 and mounted to the pipe to close end 38 .

End 36 of tubular screen 34 is preferably star-crimped closed. Star-crimping is known in the prior art. End 38 of tubular screen 34 axially overlaps the outlet pipe in concentric relation and is crimped thereto by a crimp ring 40 . Crimp rings are known in the prior art. Interior portion 26 of the exhaust pipe includes an inner tube 42 , and an outer tube 44 spaced radially outwardly of inner tube 42 and in some embodiments forming a resonator chamber 46 therebetween filled with packing material 48 . Outer tube 44 is selected from appropriate gauge metal to be deformably crimpable by crimp ring 40 . Outer tube 44 extends from flange 22 inwardly into housing 12 . Flange 22 has an opening 50 with an inner diameter and receiving inner tube 42 . Flange 22 has an inner face 52 extending radially outwardly from opening 50 and facing into housing 12 . Outer tube 44 has a first end 54 abutting and welded to inner face 52 of flange 22 and having a diameter greater than the noted inner diameter of opening 50 and spaced radially outwardly of opening 50 . Portions 26 and 28 of exhaust pipe 24 are welded to each other and to flange 22 at opening 50 . Outer tube 44 has a second distally opposite end 56 having a smaller diameter than the noted first end 52 of outer tube 44 and abutting inner tube 42 at an axial location between crimp ring 40 and inner end 32 of interior portion 26 of the exhaust pipe.

Screen 34 is spot welded along a seam 58 between ends 36 and 38 to maintain its tubular shape and prevent leakage. Screen 34 is also preferably spot welded at star-crimped end 36 including along the radial spokes 60 thereof, to maintain the star-crimping. Screen 34 at end 38 is initially open, FIG. 4, and is axially slidable along the exhaust pipe and is closed and mounted thereto only by crimp ring 40 , without welding.

The present invention in combination enables a screen-type spark arrestor to be placed over the exhaust tube to block carbon particles, and preserve performance as well as reducing cost. The use of the star-crimp construction and the crimp ring keeps the cost down and the performance up. The construction allows the use of screen material chosen to meet the noted USDA Standard 5100-1b, namely that the screen have a plurality of openings having a cumulative area greater than 200% of the radial cross-sectional area of the exhaust pipe. The crimp ring 40 is desirable to attach the screen to the exhaust pipe since a conventional weld or spot-weld is not easily manufacturable. The crimping down of the ring, FIG. 6, to a smaller diameter at area 62 eliminates the need for welds while simplifying the construction and increasing productivity and reducing cost.

It is recognized that various equivalents, alternatives and modifications are possible within the scope of the appended claims.